Hi all,

I’ve encountered some unexpected behavior when constructing a PlaneSurface when one interval’s parameters are sorted in decreasing order, like `Interval(4, 0)`

, it doesn’t seem to like this.

for example:

```
new PlaneSurface(Plane.WorldXY, new Interval(4, 0), new Interval(0, 2));
```

creates a plane with X-extends between 0 and 1. the Y is correct. However if I flip the X parameters:

```
new PlaneSurface(Plane.WorldXY, new Interval(0, 4), new Interval(0, 2));
```

then the result is correct, a surface between 0…4 in the X, and 0…2 in the Y

I tried searching PlaneSurface documentation, but I can’t find a mention of “Interval must be increasing”. But, to be honest, even if this is the requirement, I wouldn’t expect that a violation of this requirement resulted in a valid surface but that it silently changed the domain for me.

But, I feel a bit crazy, is this error on my end? Can someone run a quick test to see if you get the same result?

Thank you!